1. Field of the Invention (Technical Field)
The present invention is directed to the in vivo fusing and/or welding of bone in a fluid medium, particularly useful in endoscopy procedures.
2. Background Art
Note that the following discussion refers to a number of publications by author(s) and year of publication, and that due to recent publication dates certain publications are not to be considered as prior art vis-a-vis the present invention. Discussion of such publications herein is given for more complete background and is not to be construed as an admission that such publications are prior art for patentability determination purposes.
The medical arts do not at present provide a consistent and useful procedure for fusing or welding bone in vivo in a fluid medium, such as during endoscopy procedures. Further, since all in vivo healing and cellular processes occur in a fluid medium and are dependant upon tissue hydration, the prior art does not provide for fusing or welding bone in such fluid circumstances and further where damage to native host tissue is to be avoided.
U.S. Pat. No. 5,498,259, entitled “Method for Fusing Bone” to Mourant, et al. (“Mourant”), is directed to fusing bone by chemically removing the mineral matrix from a thin layer of the surfaces to be joined and then heating the joint using electromagnetic radiation. However, the Mourant process is conducted in vitro, uses a laser, is not conducted in a fluid medium necessary for in vivo or endoscopic use, and does not achieve weld strengths sufficient for in vivo clinical application. Further deficiencies of Mourant are discussed below.
U.S. Pat. Nos. 5,824,015 and 5,749,895 and 5,669,934, to Sawyer, et al., describe joining soft tissues, particularly those with lumens such as arteries, utilizing a surface-applied pre-formed film or sheet of collagen that is treated with electromagnetic energy. The method of union is fundamentally different whereas the substance joining the soft tissue acts like an adhesive tape. This process as disclosed does not apply to hard tissues such as bone, due primarily to the unique structure of bone and to limited weld strengths demonstrated that are insufficient for in vivo use.
U.S. Pat. No. 6,033,654, to Stedronsky, et al., describes joining soft tissue with a proteinaceous recombinant non-biologic polymer adhesive. Tissue apposition is achieved and held during the healing process. The invention is not applicable to bone. The present invention is not directed to an adhesive, but rather a welding process that creates a biologic “grout” construct that interdigitates with cancellous bone providing a mechanical construct for fusion/welding and that does not interfere with healing responses.
U.S. Pat. No. 5,955,514, to Huang, et al., describes a means to join non-biologic implants such as metal and ceramic to biologic materials such as hard tooth material with non-biologic polymer cement. The present invention does not relate to non-biologic implants such as metal or ceramic but rather to fusing normal tissue to normal tissue, rather than fusing bone to metal or ceramic.
U.S. Pat. Nos. 5,885,292 and 5,741,261, to Moskovitz et al., relate to spine surgery rather than endoscopy. Specifically, the means (instrumentation) to achieve a bone fusion is simply providing bone graft to the spine location with specific tools described.
U.S. Pat. No. 5,788,976, to Bradford, relates to spine surgery rather than endoscopy. This is a technique for harvest and preparation of the autologous cancellous bone graft. Bradford harvests the graft and separates the constituent elements by centrifuging the material and then uses a portion for treatment. The present invention does not present a bone graft harvest method per se but rather treatment of harvested bone graft. Bradford can make a paste but simply as a delivery method rather than as a means to weld. Bradford simply wants to introduce bone graft to an area, limiting harvest sequelae and allowing the benefits of bone graft to occur at a fusion site. The present invention seeks a structural weld obviating other fixation devices. The autologous graft in the present invention is treated mechanically, chemically, and electromagnetically.
U.S. Pat. No. 5,584,863, to Rauch, et al., U.S. Pat. No. 5,014,699, to Pollack, et al., and U.S. Pat. Nos. 4,266,533, 4,266,532, and 4,105,017, to Ryaby, et al., relate to electrotherapy, a different process than electromagnetic energy or radio frequency delivery to tissue during surgical or electrosurgical procedures.
U.S. Pat. No. 5,458,596, to Lax, et al., U.S. Pat. No. 6,149,620, to Baker, et al., and U.S. Pat. No. 6,159,194, to Eggers, et al, collectively relate to radio frequency or electromagnetic energy delivery to soft-tissue derived collagen rather than bone-derived collagen. Specifically described in these filings are the treatment and/or contraction of “soft tissue”, “soft tissue collagen”, or “soft tissue derived collagen” by applying radio frequency or electromagnetic energy via a conductive medium. The use of these descriptors in these Patents indicates the distinction between soft tissue-derived and bone-derived collagen further reflecting the non-obvious nature of the present invention utilizing radio frequency or electromagnetic energy during surgical or electrosurgical procedures to treat bone-derived collagen or bone-derived material. Further distinctions are discussed below.
U.S. Pat. No. 3,982,017, to Thiele, relates to specifically designed injectable solutions to aid fracture healing. The present invention utilizes other non-injectable healing aides, such as growth factors, that can be added to the fusing or welding process to augment healing.
U.S. Pat. Nos. 5,516,533 and 5,352,463, to Badylak, et al., relate to soft tissue derived grafts, not bone-derived grafts.
Laser welding of bone as described by Mourant has provided some optimism that the Holy Grail of bone fixation can be achieved, i.e., to obtain normal bone at union sites with no sequelae of fixation devices. In such a scenario, the resultant bone-bone interface would become a normal bone construct after healing. However, results utilizing current techniques as disclosed in prior art have not been successful in attaining these goals, have not been practical in vivo, and, therefore, have not been transferred to clinical application and patient care.
Bone healing occurs via natural processes when mechanical stability and apposition (i.e. compression) are combined with an adequate host healing response. Without both of these mechanical and biologic environments, healing will be impaired. To this end, both components, stability/compression and healing response, can be, and have been, modified, altered, or stimulated by various methods to assist in the host in vivo healing response. Any fusing or welding process should be attentive to both of these fundamental concerns if such processes are to be used clinically or conducted in vivo. Bone fusion or welding has been accomplished in vitro by delivering electromagnetic energy to the bone segments that require fixation after acid treatment. However, the deficiencies of such prior art have obviated use in vivo. The limited bone fusion/welding strength and duration (including decay) that has been achieved (even with application of specific “solders”), the inability to perform fusion/welding in a fluid (in vivo or during endoscopy) environment, and the limited applicability of laser energy to current treatment approaches (regulatory and safety issues, licensing and certification requirements, high equipment costs not amenable to general clinical practice, and issues of collateral damage during tissue application) have reduced the current techniques disclosed in prior art to an in vitro experiment. These techniques do not allow fusion/welding fixation without other supplementary fixation devices and have not been applicable in a fluid and/or in vivo environment.
Provisional fixation techniques are required in orthopedic treatments to hold tissue (bone sections or fragments) in specific positions until adequate, mature healing responses can be developed by the host organism that supercedes the requirement of the provisional fixation initially utilized. Specific to the techniques of the method of fusing bone as stated in Mourant, “after 16–24 hours of immersion in saline solution, however, the union held less than 500 g before failure”. This strength, and the decay of this strength in a fluid environment, is not adequate for use in an in vivo environment without additional provisional fixation techniques and more specifically under endoscopy conditions that typically involve a fluid medium. Mourant indicates the need for “external fixation devices [to be] applied to stabilize the bone segments”. Further, all in vivo healing and cellular processes occur in a fluid medium and are dependant upon tissue hydration (i.e. fluid). These are some of the reasons why the Mourant process has not been applied to clinical practices—it does not obviate the need for other provisional fixation techniques during the entire healing process and therefore the application of the Mourant technique is extraneous, possibly dangerous (e.g. acid treatment to host tissue if used in vivo, collateral damage from laser use such as osteonecrosis, etc.), and economically burdensome. As disclosed, the procedures serve as “an in vitro pre-provisional fixation technique”, not “an in vivo provisional fixation technique”.
The laser-dye energy direction process as used in Mourant is not amenable in vivo due to the lack of a natural insulator (see disclosure below). Tissue such as articular cartilage, fibrocartilage, bone, and ligament are adjacent to bone segments, particularly as in joints encountered during treatment such as endoscopy procedures, and can be damaged or altered by low level laser energy despite such attempts as dye-solder localization or application mode and technique constraints (B. Fink, et al., “Holmium:YAG laser-induced aseptic bone necrosis of the femoral condyle”, Arthroscopy 12:217–223 (1996); D. L. Janzen, et al., “Osteonecrosis after contact neodymium:yttrium aluminum garnet arthroscopic laser menisectomy”, American Journal of Roentgenol 169:855–858 (1997); S. R. Rozbruch, et al., “Osteonecrosis of the knee following arthroscopic laser menisectomy”, Arthroscopy 12:245–250 (1996); R. Thal, et al., “Delayed articular cartilage slough: two cases resulting from holmium:YAG laser damage to normal articular cartilage and a review of the literature”, Arthroscopy 12:92–94 (1996)). Limiting collateral damage is critical since it is by the adjacent tissue that the natural host healing responses are generated. Electromagnetic energy induced tissue injury or necrosis impairs both healing responses and the structural integrity of tissue, negatively affecting both of the fundamental components necessary for bone healing. For these reasons, another source of electromagnetic energy delivery is required for bone fusion/welding in vivo.
The prior art for bone fusion/welding has been labeled “an in vitro experiment” since the process is performed outside of the host with the subsequent intentions to re-introduce the segments back into the host for further subsequent and traditional fixation. The process involves acid and electromagnetic energy that is not biocompatible and has raised many concerns regarding iatrogenic damage during such processes if applied clinically. Maintaining structural and cellular integrity during such procedures is critical due to necessary regulatory clearance and acceptance in peer-reviewed medical circles. It is for these reasons, and others to be disclosed below, that prior art does not provide a consistent and useful procedure for fusing or welding bone in vivo in a fluid medium, such as during endoscopy procedures.